Motley Fool--Wall Street may be ignoring the continuing labor negotiations between the United Parcel Service (NYSE: UPS ) and the Teamsters, but investors should keep a very close eye on these negotiations as they unfold. There remain 12 supplemental contracts still to be voted on, and if they can't come to an agreement, the national contract will not go into effect. Further, if these contracts don't pass after a third vote, it could lead to a strike in those specific locations. Read more!